#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
using namespace std;

const int N = 1e6 + 10, INF = 0x3f3f3f3f;

string s;

int coun(int l, int r)
{
    int cnt = 0;
    for (int i = l;i <= r;i++) if (s[i] == 't') cnt++;
    return cnt;
}

void solve()
{
    cin >> s;

    int n = s.length();
    s = " " + s;

    long double ans = 0;
    for (int l = 1;l <= n;l++) if (s[l] == 't')
        for (int r = l + 2;r <= n;r++) if (s[r] == 't') {
            int cnt = coun(l, r);
            ans = max(ans, max(1.0l * (cnt - 2) / (r - l + 1 - 2), 0.0l));
        }
    cout << fixed << setprecision(12);
    if (ans == INF) cout << 0;
    else cout << ans;
}

signed main()
{
    //ios::sync_with_stdio(0);
    //cin.tie(0);cout.tie(0);
#define ONLINE_JUDGE
#ifndef ONLINE_JUDGE
    std::istringstream in(R"()");
    std::cin.rdbuf(in.rdbuf());
#endif
    int T = 1;
    //cin>>T;
    for (int i = 1;i <= T;i++) {
        solve();
    }
}